Provide a fixit when taking the address of an unqualified member function.

This only applies if the type has a name. (we could potentially do something
crazy with decltype in C++11 to qualify members of unnamed types but that
seems excessive)

It might be nice to also suggest a fixit for "&this->i", "&foo->i",
and "&foo.i" but those expressions produce 'bound' member functions that have
a different AST representation & make error recovery a little trickier. Left
as future work.

llvm-svn: 165763